Don't know anything about Kubota coolant requirements but I switched over to ELC coolants on all the vehicles I service. My favourite is Detroit Diesel PowerCool Plus which I believe is the same as Peak Final Charge.
2006 GMC Sierra 4.3l, NV3500,G80 locker rear, Formula Shell Synthetic 5W30, Wix 51036, Dexcool.
1987 BMW R80
Staying out of the right lane a lot.